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tipsy - formats used in TIPSY package


The TIPSY ARRAY format was originally an ascii format where the first line contains the number of elements of a 1 dimensional array, followed by all elements.

The TIPSY VECTOR format is an ascii format where the first line contains the number of elements of the 3 dimensional vector, followed by all elements, one vector at a time (but split of 3 lines).

The TIPSY binary format is the more common format. Its binary header (28 or 32 bytes, perhaps padded to 32) contains the time and number of bodies (see below).


Here is a TIPSY VECTOR format of the origin, unit X, Y and Z vectors on a 3-dimensional cube.



The header is 28 bytes in Tipsy’s original code/defs.h, however, many authors are padding this with a integer version, making it 32 bytes. This also limits the number of particles, see CAVEAT below.

struct header {
    double time ;
    int nbodies ;     // total number of bodies
    int ndim ;        // always 3
    int nsph ;        // number of gas particles
    int ndark ;       // number of dark/halo particles
    int nstar ;       // number of star particles
    int version ;     // a new 32-byte padding field not used by all tipsy
I/O projects
} ;


Only works in 3-dimensional space, and only 3 flavors of particles (gas, dark, star) are supported. For comparison, the gadget(5NEMO) format (version 1/2/3) supports 6 flavors of particles, though the last one is never used (but never say never).

Since the 32 byte header contains a few 4-byte integers, this limits the total number of particles to ~2 billion, unless the parser is recoded to use unsigned int, in which case ~4 billion can be used.

See Also

tipsy(1) , snapshot(5NEMO)


Peter Teuben


nemo/src/nbody/io/tipsydefs.h      definition of the TIPSY binary format 
bonsai/runtime/include/tipsydefs.h    Bonsai’s view (with some fields changed
type) [no version]
tipsy/code/defs.h    Original definition [no version]
uns_projects/lib/utils/tipsydefs.std.h    [no version]
Note that Bonsai has hyjacked the Phi field for dark and stars for an integer ID. With the -DWITH_BOOM you can currently carry a new acc/epot in version 6 of the tipsy files

Update History

23-dec-1994    man written    PJT
5-feb-2022    document some historic confusion    PJT

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